1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing an optical recording medium in which ratios of spare area to data area differ from one zone to another, depending on each zone""s location in the radial direction, and which has information needed to discriminate data area and spare area in each zone, and to a method and apparatus for writing/reproducing data to/from the optical recording medium.
2. Description of the Related Art
Optical discs have come into wide use since the advent of CD (compact disc). The demand for optical discs is expected to grow steadily with popularization of DVD (digital versatile disc). Optical discs include read-only discs such as CD-ROM and DVD-ROM, write-once discs such as CD-R and DVD-R, and rewritable discs such as CD-RW and DVD-RAM. Standard formats of CD-RW and DVD-RAM have been released and standardization for DVD-R is in progress.
As shown in FIG. 1, the rewritable physical area of DVD-RAM has a lead-in area, a user area, and a lead-out area. The user area is divided into 24 contiguous groups, so-called zones, and guard areas are situated before and behind each zone. Each zone is made up of a data area for recording data and a spare area for replacing a defective portion of the data area.
The data area is made up of a plurality of ECC (error correction code) blocks, each consisting of 16 sectors. The location of each sector is specified by a physical sector number (PSN) that is given uniquely to each sector. That is, a PSN is assigned to every sector from the inner diameter to the outer diameter. While recording, LSNs (logical sector number) are assigned to only non-defective sectors sequentially.
Tracks located in the same zone have an equal number of sectors. As the track length is increased by the angular length per sector from inside out, the number of sectors per track is increased by 1 and a new zone identification number is assigned. For every zone, CLV (constant linear velocity) is employed, but CAV (constant angular velocity) is used for tracks within the same zone.
For rewritable optical discs such as DVD-RAM, defects that arise in their recording surface should be managed to achieve highly reliable write/reproduction operation in a manner that data is not written to sectors in which read-out errors are detected beyond a predetermined level (hereinafter referred to as xe2x80x9cdefectivexe2x80x9d or xe2x80x9cbadxe2x80x9d sectors). To accomplish this, defect management is performed such that addresses of defective sectors are stored in defect management tables on the optical disc and access to data on such defective sectors is prohibited. As shown in FIG. 2, if a defective sector is detected during a write operation, it is replaced by the next valid sector (slipping replacement). When a bad sector is detected during a reproduction operation, an ECC block containing the bad sector is replaced by a unused ECC block in a spare area, as shown in FIG. 3 (linear replacement).
Defect management information, or physical addresses of defective sectors within the data area are stored in a DMA (defective management area), which is provided in four places, two in a lead-in area and the other two in a lead-out area, as shown in FIG. 1, to protect against the defects which may arise in the four DMAs themselves.
The DMA is made up of two ECC blocks, or 32 sectors. The first ECC block consists of one sector for a DDS (disc definition structure) and 15 other sectors for a PDL (primary defect list). Sixteen sectors of the second ECC block are all used for a SDL (secondary defect list).
As shown in FIG. 4, each track of DVD-RAM is, physically, made up of a recording portion A for recording user data and a header portion B for providing positional information and indicating whether the track is a groove track or land track. Groove tracks and land tracks are arranged alternately, and wobble boundaries C are formed between groove tracks and land tracks. The wobble shape of the boundary C is used to generate a periodic signal of low frequency and thus provide a channel clock for detection of signal from the optical disc while the optical disc is rotated in the CAV mode.
For the optical disc described above, in the conventional art, a ratio of spare area to data area is provided equally for every zone, about 5%, as shown in FIG. 5A. A zone has 875 more sectors than the next most-inwardly located zone because every zone has 875=(21000 tracks/disc)/(24 zones/disc) tracks and the number of sectors per track is increased by 1 for every track. Hence, more spare area is provided for zones near the outer radii than for zones near the inner radii.
However, as shown in waveform 51 of FIG. 5A, experimental observations shows a tendency that more defects arise in zones near the inner or outer radii than in zones near the central radii because of problems of deposition by sputtering in the disc manufacturing process. The waveform 51 of FIG. 5(a) is parabolic.
Hence, in case where a constant ratio of spare area to data area is set to every zone, as shown in waveform 50 of FIG. 5A, it may happen that, while zones near the inner or outer radii run short of the spare area for replacement of defective areas on the data area, a large amount of spare area is not used in the zones near the central radii.
Moreover, in a conventional disc, there exists a ratio between the size of the spare area and data area that is maintained constant throughout the disc. Thus, conventional systems can recognize the boundary between the data area and the spare area without referring to any stored information concerning that boundary because the boundary has already been fixed by DVD disc physical specifications and can be calculated by a program in which the constant ratio is considered.
But, if the boundary is varied and boundary information is not written on a disc, the system can neither recognize exact boundary nor calculate boundary information by any program.
One object of the invention is to record boundary information in a predetermined location on a disc so that a system can recognize it and perform the proper operation of recording, reproduction and replacement of defective areas when the position of a boundary between the spare area and the data area is varied, which object is not limited to a disc having a plurality of zones or a constant ratio between the spare area and data area.
It is an object of the present invention to provide a method and apparatus for manufacturing an optical recording medium in which the ratio of a spare area to a data area varies according to the radial range of the corresponding zones, respectively, and which has information in a predetermined area of said medium needed to discriminate between a data area and a spare area.
It is another object of the present invention to provide a method and apparatus for writing/reproducing data to/from said optical recording medium in which the ratio of the spare area to the data area varies according to the radial range of the corresponding zones, respectively, and has information in a predetermined area of said medium needed to discriminate between the data area and the spare area.
To achieve these and other objects, the present invention provides a method and apparatus for manufacturing an optical recording medium, the recording area being made up of a plurality of zones and having a data area and a spare area and information needed to discriminate among the data area and the spare area. According to the method and apparatus, in one or more zones, the ratio of the spare area to the data area varies depending on the corresponding locations or those areas relative to the optical recording medium. Information needed to discriminate a data area and from a spare area, e.g., boundaries between the two areas which are changed with the ratios, is written as a physical shape or as a normally written signal into a predetermined area on the optical recording medium.
In the method and apparatus for writing data to said optical recording medium having information needed to discriminate among the data area and the spare area according to the present invention, the ratio of spare area to data area varies depending on the relative location of the zones on the optical recording medium. Information needed to discriminate a data area from a spare area, e.g., the boundary between the two areas, is recorded on a predetermined area on the optical recording medium. Thereafter, when a write operation requested, the boundary information is used to locate the appropriate area.
In the method and apparatus for reproducing data from an optical recording medium having information needed to discriminate the data areas from the spare, area according to the present invention, information needed to discriminate a data area from a spare area, the boundary between the two areas, is read out from a predetermined area on the optical recording medium. Referring to the boundary information, data recorded in the data area is reproduced and data allocated to defective areas on the data area is moved into the corresponding region of the spare area for replacement.
The foregoing and other objectives of the present invention will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.